Known rotation transmission devices for selectively allowing and prohibiting transmission of torque from a driving shaft to a driven shaft include one having a two-way clutch which can be engaged and disengaged by an electromagnetic clutch.
The below-identified Patent document 1 discloses a rotation transmission device including a two-way clutch which is selectively engaged and disengaged by an electromagnetic clutch. This two-way clutch includes a control retainer and a rotary retainer both having bars disposed between an outer ring and an inner ring provided inside of the outer ring, and arranged such that the bars of one of the retainers circumferentially alternate with the bars of the other retainer, thereby defining pockets between adjacent bars. A pair of rollers are mounted in each pocket, and biased away from each other by an elastic member mounted therebetween to a stand-by position where the rollers engage a cylindrical surface formed on the inner periphery of the outer ring, and cam surfaces formed on the outer periphery of the inner ring, whereby when the inner ring is rotated in one direction, one of each pair of rollers become wedged between the cylindrical surface and the corresponding cam surface, so that the rotation of the inner ring is transmitted to the outer ring.
The electromagnetic clutch for controlling the two-way clutch includes an electromagnet configured, when energized, to move the control retainer in an axial direction. When the control retainer is moved in the axial direction, the control retainer and the rotary retainer are rotated relative to each other in the direction in which the circumferential widths of the pockets decrease, by the action of a torque cam, as a motion converting mechanism, provided between the opposed surfaces of a flange of the control retainer and a flange of the rotary retainer. As a result, the pairs of rollers are moved to the disengaged positions by the bars of the respective retainers, thus prohibiting transmission of rotation from the inner ring to the outer ring.
In this rotation transmission device, when the electromagnet of the electromagnetic clutch is de-energized, the control retainer and the rotary retainer are rotated relative to each other in the direction in which the circumferential widths of the pockets increase, so that the opposed pairs of rollers instantly engage the cylindrical surface and the cam surfaces. That is, since there exists very little looseness in the rotational direction, responsiveness of the two-way clutch is excellent.